Increasing the fish oil content in tilapia feeds was shown, in the
present study, to significantly increase the n-3 content in the dorsal
muscle of farmed tilapia. Similar results have been obtained
using diets enriched with n-3-rich plant oils. Justi et al.(2003)
and Visentainer et al.(2005) reported that, feeding Nile tilapia diets
containing linseed oil, which is rich in 18:3n-3, can increase the
linolenic acid, EPA and DHA content of fillets when substituted
against sunflower oil, which is rich in 18:2n-6. It may therefore
be beneficial to include n-3-rich plant oils, or fish oils, in commercial
tilapia feeds formulated for use in intensive systems where fish
have little or no access to phytoplankton (Karapanogiotidis et al.,
2007). Recent studies with adult Nile tilapia have shown that
45 days is the shortest time required for the inclusion of flaxseed
oil to significantly increase the total n-3 and DHA content of tilapia
muscle (Tonial et al., 2009). To reduce the additional costs associated
with the use of fish oil, additional feeding strategies have been
proposed. These include feeding tilapia on diets containing flaxseed
oil through most of their farmed production and then switching
to a fish oil-based diet as the fish approach harvestable size